The present application hereby claim foreign priority benefits under Title 35, United States Code, xc2xa7119 to French Patent Application No. 01 04728, filed Apr. 6, 2001.
The present invention related generally to instruments and methods for spinal stabilization, and more particularly to spinal plating systems and methods.
Various types of plating devices and systems have been used to stabilize portions of the spine. For cases in which interbody fusion is desired in the lumbro-sacral region, stabilization using posterior plating has been preferred by many surgeons for good fixation and to avoid damage to the vascular and nervous system components adjacent the anterior surfaces of the L5 vertebra. A posterior plating system for stabilization of the L5-S1 junction is disclosed in U.S. Pat. No. 5,127,912 issued Jul. 7, 1992 to Ray and Ashman.
While posterior fixation systems are often used in fusions, the anterior surgical approach for insertion of fusion devices is preferred from several perspectives. Less blood loss and reduced post-operative pain can be achieved, and there is risk of traumatizing nerves. Additionally, the posterior approach impairs muscles, which are vascularized, and ligaments, which are cut. Effective anterior plating could generally avoid the risks associated with posterior surgery, particularly if an anterior approach is used which is also as minimally invasive as possible, since it is then only necessary to move aside soft tissues which do not affect the stability of the spinal column.
There is however one zone of the spine where an anterior approach entails a particular risk: the zone corresponding to lumbar vertebrae L4-L5 and the first sacral vertebra S1. In this region, the aorta and the vena cava divide to form the right and left iliac veins and arteries. There is therefore a risk of damaging an important blood vessel during implantation of a conventional fixation system. There is also a risk that important blood vessels could be damaged by screw backout, or simply by protrusion of the plate against the blood vessel. Moreover, between the profiles of vertebrae L5 and S1 there is an angle called the xe2x80x9cpromontory anglexe2x80x9d which is very variable from one individual to another. There can also be sliding between L5 and S1 (spondylolisthesis). These conditions further increase the difficulty and risk factors associated with attachment of a stabilization device anteriorly to the L5-S1 region.
There remains a need for anterior plating systems and methods to provide stability for fusion between vertebrae that is adapted to address the challenges presented above.
Described briefly according to the illustrated embodiments of the invention, a stabilizer for the lumbar/sacral junction is provided. The stabilizer includes a plate having a generally triangular shape with an upper node and a pair of lower nodes. The upper node has an upper hole to receive a screw for passage into an upper vertebra, such as L5 . The lower nodes each include a hole to receive a screw for passage into a lower vertebra, such as S1.
There is also provided a plate for a device for stabilization of vertebrae L5 and S1 that has a generally triangular shape, and includes near its upper vertex, a hole through which a screw is passed for fixing the plate to L5, and two holes situated near its lower vertices through which screws are passed for fixing the plate to S1.
The present invention also provides an anterior spinal plate system that has a plate with a generally triangular shape and includes on its posterior face a protrusion which extends along at least part of the width of the plate that bears against the lower anterior lip of the lower endplate of L5.
The present invention additionally provides an anterior spinal plate system that has a plate with a triangular shape and includes, on its posterior face near its lower vertices, protrusions which are intended to come to bear against the lower margin of the salient part of S1. The plate can further include on the edge of its posterior face, in the region of its upper vertex, a ridge-shaped protrusion or at least one anchoring point or spike to contact or anchor in L5.
The present invention further provides an anterior spinal plate system that has a plate with an upper face, a lower face, and at least one hole therethrough extending between the upper and lower faces. A retaining element extends from the upper face of the plate adjacent the at least one hole. The retaining element has a first form wherein a screw is insertable into the at least one hole and is formable to a second form wherein at least a portion of the retaining element extends over the at least one hole, blocking the screw in the hole.
The present invention further provides an anterior spinal plate system that includes a plate having a triangular shape and an upper face, a lower face, and holes therethrough extending between the upper and lower faces at each vertex. A retaining element is provided to prevent screw backout. In one form, the retaining element can be clipped, screwed or otherwise secured to the anterior face of the plate and is capable of at least partially covering the holes passed through by the screws. The retaining element can be of substantially circular shape, substantially triangular shape, or spoke shaped.
The invention also provides a system for osteosynthesis of the spine for joining vertebrae L5 and S1. The system includes a triangular plate having an upper vertex oriented over L5 and two lower vertices oriented over S1. Each vertex has a hole through which a screw may be passed. The system further includes an interbody device inserted into the disc space separating L5 and S1.
The present invention further contemplates instruments for use during surgical procedures that are used to secure an anterior supplemental fixation plate to the spine. One such instrument includes a plate holder that includes a holding portion mounted on a shaft. The holding portion matches the shape of the lower edge of the plate and is provided with means for establishing and maintaining a defined relative position between the holding portion and the plate. The instrument further includes a support member having guiding portions for directing screws into the plate holes.
The present invention further includes methods for stabilizing a spinal segment. One method includes installing a generally triangular-shaped plate having an upper node along the anterior face of L5 and a pair of lower nodes along the anterior face of S1; installing a first screw from the front of the plate through a single hole in the upper node of the plate into L5; and installing screws from the front of the plate through a hole in each of the lower nodes of the plate and into S1. Variations to the above method and other methods are also contemplated.
The above is intended merely as a summary of various inventive aspects presented in the present application, and is in no way intended to be an exhaustive or all-inclusive recitation of such aspects. Additional aspects, forms, features, embodiments and principles of the present invention will be further described below.